ol8b03214_si_001.pdf (1.02 MB)
Silver-Catalyzed tert-Butyl 3‑Oxopent-4-ynoate π‑Cyclizations: Controlling the Ring SizeHydroxypyrone or Pulvinone Formationby Counterion and Additive Optimization
journal contribution
posted on 2018-11-16, 17:30 authored by David Hermann, Reinhard Brücknertert-Butyl 2,5-diaryl-3-oxopent-4-ynoates,
obtained
from arylacetylenes and the acid chloride of tert-butyl 2-phenylmalonate, represent strongly enolized β-ketoesters.
Their CC bonds were activated by Ag(I) salts so that de-tert-butylating π-cyclizations occurred. The latter
followed a 6-endo-dig mode giving
3,6-diaryl-4-hydroxy-2-pyrones, or a 5-exo-dig mode giving (Z)-configured 2-aryl-4-(arylmethylidene)tetronic
acids (“pulvinones”). Perfectly selective pyrone formations
were induced by AgSbF6 in methanol and equally selective
pulvinone formations by Ag2CO3 and DABCO in
acetonitrile.